Magnesium alumosilicate-based phosphor

ABSTRACT

The invention relates to co-activated magnesium alumosilicate based phosphors, to a process of its preparation, the use of these phosphors in electronic and electro optical devices, such as light emitting diodes (LEDs) and solar cells and especially to illumination units comprising said magnesium alumosilicate-based phosphors.

TECHNICAL FIELD

The invention relates to co-activated magnesium alumosilicate basedphosphors, to a process of the preparation of these phosphors, the useof these phosphors in electronic and/or electro optical devices, such aslight emitting diodes (LEDs) and solar cells, and especially toillumination units comprising said phosphors.

BACKGROUND ART

White light-emitting diodes (LEDs) exhibit high efficiency, longlifetimes, less environmental impact, absence of mercury, short responsetimes, applicability in final products of various sizes, and many morefavorable properties. They are gaining attention as backlight sourcesfor liquid crystal displays, computer notebook monitors, cell phonescreens, and in general lighting.

As known to the expert, white LEDs can be obtained by adding a yellowemitting phosphors, such as YAG:Ce, which exhibits an emission peakwavelength around 560 nm, to a blue light emitting LED. The emitted peakwavelength of corresponding blue light emitting LEDs is typically in therange from 450 to 470 nm. Therefore, only a limited number of phosphorscan be used in order to obtain white LEDs because the phosphors need toabsorb light in the range emitted from the blue LED.

By combining red, green, and blue emitting phosphors with an near UVLED, which typically emits light at a wavelength ranging from 280 to 400nm, as a primary light source, it is possible to obtain a tri-colorwhite LED with better luminescence strength and superior white color incomparison to the above described white LEDs. Consequently, there is aconsiderable demand for phosphors excitable at wavelength ranging from280 nm to 400 nm.

To obtain such white LEDs by using UV-LEDs or near UV-LEDs, typically ared, a green, and a blue emitting phosphor are first mixed in a suitableresin. The resultant gel is then provided on a UV-LED chip or a nearUV-LED chip and hardened by UV irradiation, annealing, or similarprocesses. The phosphor mixture in the resin should be as homogeneouslydispersed as possible in order to observe an even, white color, whilelooking at the chip from all angles. However, it is still difficult toobtain a uniform distribution of the different phosphors in the resinbecause of their different particle sizes, shapes and/or their densityin the resin. Hence, it is advantageous to use less than three phosphorsor even only one phosphor. For example, the use of a phosphor having twoor more main emission peaks at different wavelengths represents apotential solution of the above-mentioned problem.

In this connection, Sung Hun Lee, Je Hong Park, Se Mo Son, and Jong SuKima disclose in Appl. Phys. Lett. 2006, 89, 221916, a CaMgSi₂O₆:Eu²⁺,Mn²⁺ phosphor exhibiting three emission bands peaks at around 450 nm,580 nm, and 680 nm with main peaks at 440 nm and 680 nm. Since the mostpreferred spectral range for a human eye is between 400 and 650 nm, theemission peak at 680 nm is located on the edge of the visible range.Moreover, a mixture of green-poor CaMgSi₂O₆:Eu²⁺, Mn²⁺ andgreen-to-yellow emissive (BaSr)₂SiO₄:Eu²⁺ is needed in order to achievewhite light having correlated color temperatures from 4845 to 9180 K andcolor rendering indices from 71% to 88%.

However, even by using a mixture of two phosphors, in order to producewhite LEDs using UV or near UV-LEDs, it is still difficult to uniformlymix phosphors having different sizes, particle shapes and densities inthe resin. Moreover, the phosphors should not be excited by a wavelengthlocated in the visible range. For instance, if the emission spectrum ofthe green phosphor overlaps with the excitation spectrum of the redphosphor, then color tuning becomes difficult. Additionally, if amixture of two or more phosphors is used to produce white LEDs using ablue emitting LED as the primary light source, the excitation wavelengthof each phosphor should efficiently overlap with the blue emissionwavelength of the LED.

An example of a white LED using UV or near UV-LED as the primary lightsource and the use of only one phosphor is given by Woan-Jen Yang,Liyang Luo, Teng-Ming Chen, and Niann-Shia Wang in Chem. Mater., 2005,17 (15), 3883-3888. The authors describe an alumosilicate-based phosphorof the general formula CaAl₂Si₂O₈: Eu²⁺, Mn²⁺, exhibiting a mainemission peak centred at 425 nm and a broad emission band centred at 586nm.

Another example of a white LED comprising a UV or near UV-LED primarylight source and only one phosphor is given in US 2010/0259161 A, whichdiscloses a co-activated phosphor based on the formula CaMg₂Al₆Si₉O₃₀.The main emission peaks of the described phosphor are centred at 467 nmand 627 nm, respectively. However, the emission ranges up to 800 nm,which is outside of the range most sensitive to the human eye.

Accordingly, there is still room for improvements and modern luminescentmaterials, preferably

-   -   exhibit high colour rendering indices,    -   exhibit at least two emission bands in the range of the        VIS-light, preferably in the range of the VIS light which is in        particular most sensitive to the human eye,    -   are effectively excitable by an UV or near UV emitting primary        light source,    -   exhibit high quantum yields,    -   exhibit high efficiency over a prolonged period of use,    -   have high chemical stability, preferably against humidity or        moisture    -   exhibit lower thermal quenching resistivity    -   are obtainable by method of production, which has to be cost        efficient and especially suitable for a mass production process.

In view of the cited prior art and the above-mentioned requirements onmodern luminescent materials, there is still a considerable demand foralternative materials, which preferably do not exhibit the drawbacks ofavailable phosphors of prior art or even if do so, to a less extend.

DISCLOSURE OF INVENTION

Surprisingly, the inventors have found that co-activated magnesiumalumosilicate based phosphors represent excellent alternatives toalready known phosphors of the prior art, and preferably, improve one ormore of the above-mentioned requirements in view of the prior art, ormore preferably, fulfil all above-mentioned requirements at the sametime.

Besides other beneficial properties, the phosphors according to thepresent invention exhibit upon excitation by UV or near UV radiation atleast two main emission peaks in the range of VIS-light, preferably inthe VIS light range which is most sensitive to the human eye. Moreover,they exhibit a low thermal quenching resistivity, have high chemicalstability, and have high colour rendering properties.

Thus, the present invention relates to a compound of formula I,(M)(Mg_(1-z)Al_(z))(Si_(2-z)T_(z))O₆: at least two of ABC  I

-   wherein,-   M denotes at least one alkaline earth element selected from Ca, Sr,    or Ba,-   T denotes at least one trivalent element selected from Al, Ga, In,    or Sc,-   A and B denote, each differently from another, a divalent element    selected from Pb²⁺, Mn²⁺, Yb²⁺, Sm²⁺, Eu²⁺, Dy²⁺, or Ho²⁺, and-   C denotes a trivalent element selected from Y³⁺, La³⁺, Ce³⁺, Pr³⁺,    Nd³⁺, Pm³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺,    Lu³⁺, or Bi³⁺, with the proviso that at least two elements selected    from A, B or C have to be present,-   and-   0<z<0.75.

The invention further relates to a method for the production of thecompounds according to the present invention, the use of a compoundaccording to the present invention as a conversion phosphor convertingall or some parts of a UV or near UV radiation into longer wavelength,mixtures comprising at least one compound according to the presentinvention; the use of a compound according to the present invention or amixture comprising a compound according to the present invention inelectronic and/or electro optical devices, such as light emitting diodes(LEDs) and solar cells, and especially to illumination units and LCDbacklights comprising the compounds according to the present invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a XRD pattern (measured by the wavelength Cu_(Kα)) of(Ca_(0.8))(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆:(Mn²⁺)_(0.2)(Eu²⁺)_(0.2)prepared by the co-precipitation method as illustrated in Example 1.

FIG. 2 shows an emission spectrum(Ca_(0.8))(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆:(Mn²⁺)_(0.2)(Eu²⁺)_(0.2) prepared by the co-precipitation method asillustrated in Example 1 upon excitation with radiation at a wavelengthof 350 nm. The phosphor emits light having main emission maxima atapproximately 680 nm, approximately 580 nm and approximately 440 nm.

FIG. 3 shows a XRD pattern (measured by the wavelength Cu_(Kα)) of(Ca_(0.8))(Mg_(0.5)Al_(0.3))(Si_(1.7)Al_(0.3))O₆:(Mn²⁺)_(0.2)(Eu²⁺)_(0.2) preparedby the co-precipitation method as illustrated in Example 2.

FIG. 4 shows an emission spectrum of(Ca_(0.8))(Mg_(0.5)Al_(0.3))(Si_(1.7)Al_(0.3))O₆:(Mn²⁺)_(0.2)(Eu²⁺)_(0.2) prepared by the co-precipitation method asillustrated in Example 2 upon excitation with radiation at a wavelengthof 350 nm. The phosphor emits light having main emission maxima atapproximately 690 nm and approximately 560 nm.

FIG. 5 shows the XRD pattern (measured by wavelength Cu_(Kα)) of(Ca_(0.64)Sr_(0.16))(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆:(Mn²⁺)_(0.2)(Eu²⁺)_(0.2) prepared by the micro reactionsystem as illustrated in Example 3 FIG. 6 shows the emission spectrum of(Ca_(0.64)Sr_(0.16))(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆:(Mn²⁺)_(0.2)(Eu²⁺)_(0.2) prepared by a micro-reactionsystem as illustrated in Example 3 upon excitation with radiation at awavelength of 350 nm. The phosphor emits light having main emissionmaxima at approximately 680 nm, approximately 570 nm and approximately440 nm.

FIG. 7 shows the emission spectra of (Ca_(0.8))(Mg_(0.8))Si₂O₆:(Mn²⁺)_(0.2)(Eu²⁺)_(0.2);(Ca_(0.8))(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆:(Mn²⁺)_(0.2)(Eu²⁺)_(0.2) and(Ca_(0.8))(Mg_(0.5)Al_(0.3))(Si_(1.7)Al_(0.3))O₆:(Mn²⁺)_(0.2)(Eu²⁺)_(0.2)upon excitation with radiation at a wavelength of 350 nm.

FIG. 8 shows the integrated emission intensity of the phosphor ofExample 1(Ca_(0.8))(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆:(Mn²⁺)_(0.2)(Eu²⁺)_(0.2)and in comparison the integrated emission intensity of the comparativeexample (CaMgSi₂O₆: Eu²⁺Mn²⁺).

DETAILED DESCRIPTION OF THE INVENTION

In a preferred embodiment of the present invention, the compounds offormula I are selected from the compounds of formula Ia,(M_(1-x-u-p))(Mg_(1-z-v-q)Al_(z-m))(Si_(2-z)T_(z-n))O₆:A_(x)B_(y)C_(w)  Iawherein M, T, A, B and C have the same meanings as mentioned above informula I,m+n+q+p=w, whereby m≥0, n≥0, p≥0, and q≥0,u+v=y, whereby v≥0, and u≥0,0≤w<0.3,0≤x<0.5,0≤y<0.5, where at least two of the indices w, x and y are >0, and0<z<0.5.

Preferably, the compounds of formula I are selected from the group ofcompounds of formula Ia, wherein T denotes Al, and/or w=0, and/or Adenotes Eu²⁺, and/or B denotes Mn²⁺.

More preferably, the compounds according to the present invention areselected from the group of compounds of formulae Ia-1 to Ia-7,((Sr_(s)Ba_(r)Ca_(t))_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-1((Ca_(t)Ba_(r))_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-2((Sr_(s)Ba_(r))_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-3((Sr_(s)Ca_(t))_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-4(Sr_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-5(Ba_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-6(Ca_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-7,wherein,0<r<1; 0<s<1; 0<t<1; whereby r+s+t=1,u+v=y, whereby v≥0, u≥0, whereby at least one of the indices u and v,has to be larger than 0,0.1<x<0.3,0.1<y<0.3, and0.05<z<0.4.

Especially preferred compounds are selected from the group of compoundsof formulae Ia-1, Ia-2, Ia-4 and Ia-7, and more preferably from thegroup of compounds of formulae Ia-2, Ia-4 and Ia-7, wherein x, y bothare 0.15 to 0.2, and/or u is 0.

Particularly preferred compounds are selected from the group ofcompounds of formulae Ia-2a, Ia-4a and Ia-7a,((Ca_(t)Ba_(r))_(0.8))(Mg_(0.8-z),Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-2a((Sr_(s)Ca_(t))_(0.8))(Mg_(0.8-z)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-4aCa_(0.8)(Mg_(0.8-z)Al_(z))(Si_(2-z)Al)O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-7awherein,0<r<1; 0<s<1; 0<t<1, preferably 0.75<r<1; 0<s<0.25; 0<t<0.25, with theprovisos that r+t=1, and s+t=1, and0.075<z<0.3.

The compounds according to present invention, are especially suitable toconvert some or all of said UV or near UV radiation into longerwavelength, preferably into the range of the VIS light.

In the context of the present application the term “UV radiation” hasthe meaning of electromagnetic radiation having a wavelength rangingfrom approximately 100 nm to approximately 280 nm, unless explicitlystated otherwise.

Additionally, the term “near UV radiation” has the meaning ofelectromagnetic radiation having a wavelength ranging from approximately280 nm to approximately 400 nm, unless explicitly stated otherwise.

Moreover, the term “VIS light or VIS-light region” has the meaning ofelectromagnetic radiation having a wavelength ranging from approximately400 nm to approximately 800 nm unless explicitly stated otherwise.

In the context of the present application, the term “conversionphosphor” and the term “phosphor” are used in the same manner.

Preferably, the compounds according to the present invention aretypically excited by artificial or natural radiation sources in thenear-UV spectral range, preferably about 280 to about 400 nm. Thus, thepresent invention relates also to the use of compounds of formula I asconversion phosphors, or short “phosphors”.

Artificial “radiation sources” or “light sources” are preferablyselected from black lights, short wave ultraviolet lamps, gas-dischargelamps, UV-LEDs, near UV LEDs or UV-lasers.

In the context of the present application, the term “natural radiationsources” means solar irradiation or sunlight.

It is preferred that the emissions spectra of the radiation sources andthe absorption spectra of the compounds according to the presentinvention overlap more than 10 area percent, preferable more than 30area percent, more preferable more than 60 area percent and mostpreferable more than 90 area percent.

The term “absorption” means the absorbance of a material, whichcorresponds to the logarithmic ratio of the radiation falling upon amaterial, to the radiation transmitted through a material.

The term “emission” means the emission of electromagnetic waves byelectron transitions in atoms and molecules.

Preferably, the phosphors according to the present invention exhibit atleast two emission peaks in the VIS light region, while being excited byUV or near UV light. Preferably, a first emission peak having itsemission maximum preferably between about 400 nm and about 500 nm, morepreferably between about 420 nm and about 480 nm, and a second emissionpeak having its emission maximum preferably in the range fromapproximately 550 nm to approximately 625 nm, more preferably fromapproximately 560 nm to approximately 600 nm.

In another preferred embodiment, the phosphors according to the presentinvention exhibit at least three emission peaks in the VIS light region,while being excited by UV or near UV light. A first emission peak havingits emission maximum between about 400 nm and about 500 nm, morepreferably between about 420 nm and about 480 nm, a second emission peakhaving its emission maximum in the range from approximately 550 nm toapproximately 625 nm, more preferably from approximately 560 nm toapproximately 600 nm, and a third emission peak having its emissionmaximum in the range from approximately 625 nm to approximately 790 nmmore preferably from approximately 650 nm to approximately 720 nm,respectively.

The emission peaks of the compounds according to the present invention,preferably overlap each other. Preferably the overlap less than 90 areapercent, more preferable less than 60 area percent even more preferableless than 30 area percent.

By varying the amount of Al in the compounds of the present invention,especially with regards to parameter z, the relative intensity of theemission peak having its emission maximum in the range of approximately550 nm to approximately 625 nm, and the emission peak having itsemission maximum in the range of approximately 625 nm to approximately790 nm can be controlled.

Thus, it is possible to vary the emission color of the phosphor byvarying the Al content. Generally, the higher the value of z, the higheris the intensity of emission peak having its main emission maximum inthe range of approximately 550 nm to approximately 625 nm, and the loweris intensity of the emission peak having its main emission maximum inthe range of approximately 625 nm to approximately 790 nm.

Thus, preferred compounds according to the present invention arepreferably selected from compounds of the following sub formulae,((Ca_(t)Ba_(r))_(0.8))(Mg_(0.75)Al_(0.05))(Si_(1.95)Al_(0.05))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-2aa((Ca_(t)Ba_(r))_(0.8))(Mg_(0.7)Al_(0.1))(Si_(1.9)Al_(0.1))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-2ab((Ca_(t)Ba_(r))_(0.8))(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-2ac((Ca_(t)Ba_(r))_(0.8))(Mg_(0.6)Al_(0.2))(Si_(1.8)Al_(0.2))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-2ad((Ca_(t)Ba_(r))_(0.8))(Mg_(0.55)Al_(0.25))(Si_(1.75)Al_(0.25))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-2ae((Ca_(t)Ba_(r))_(0.8))(Mg_(0.5)Al_(0.3))(Si_(1.7)Al_(0.3))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-2af((Sr_(s)Ca_(t))_(0.8))(Mg_(0.75)Al_(0.05))(Si_(1.95)Al_(0.05))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-4aa((Sr_(s)Ca_(t))_(0.8))(Mg_(0.7)Al_(0.1))(Si_(1.9)Al_(0.1))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-4ab((Sr_(s)Ca_(t))_(0.8))(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-4ac((Sr_(s)Ca_(t))_(0.8))(Mg_(0.6)Al_(0.2))(Si_(1.8)Al_(0.2))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-4ad((Sr_(s)Ca_(t))_(0.8))(Mg_(0.55)Al_(0.25))(Si_(1.75)Al_(0.25))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-4ae((Sr_(s)Ca_(t))_(0.8))(Mg_(0.5)Al_(0.3))(Si_(1.7)Al_(0.3))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-4afCa_(0.8)(Mg_(0.75)Al_(0.05))(Si_(1.95)Al_(0.05))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-7aaCa_(0.8)(Mg_(0.7)Al_(0.1))(Si_(1.9)Al_(0.1))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-7abCa_(0.8)(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-7acCa_(0.8)(Mg_(0.6)Al_(0.2))(Si_(1.8)Al_(0.2))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-7adCa_(0.8)(Mg_(0.55)Al_(0.25))(Si_(1.75)Al_(0.25))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-7aeCa_(0.8)(Mg_(0.5)Al_(0.3))(Si_(1.7)Al_(0.3))O₆:(Eu²⁺)_(0.2)(Mn²⁺)_(0.2)  Ia-7afwherein, 0<r<1; 0<s<1; 0<t<1, preferably 0.75<r<1; 0<s<0.25; 0<t<0.25,whereby r+t=1, and s+t=1.

The starting materials for the preparation of the compound according tothe present invention are commercially available and suitable processesfor the preparation of the compounds according to the present inventioncan be summarized in two general process classes. First, a solid-statediffusion process, and secondly, a wet-chemical process.

In the context of the present application, the term “solid statediffusion process” refers to any mixing and firing method or solid-phasemethod, comprising the steps of mixing oxides of Mg, Al, M and one ormore salts comprising at least two elements selected from A, B or C at apredetermined molar ratio, optionally grinding the mixture, andcalcining the powders in a furnace at temperatures up to 1500° C. for upto several days, optionally, under a reductive atmosphere (cf. PhosphorHandbook, second edition, CRC Press, 2006, 341-354).

In the context of the present application, the term “wet-chemicalprocess” preferably comprises the following steps:

a) mixing a silicon-containing agent, a mixture of salts comprising atleast the elements of Mg, Al, M and T and one or more salts comprisingat least two elements selected from A, B or C at a predetermined molarratio in a solvent;

b) adding a precipitation agent;

c) performing a primary heat treatment on the mixture, preferably in atemperature range of 800 to 1300° C. under an oxidative atmosphere; and

d) performing a secondary heat treatment on the mixture preferably in atemperature range of 800 to 1300° C. under a reductive atmosphere.

The above-mentioned heat treatment in step c) and/or d) is preferablycarried out at a temperature above 1000° C., and more preferably in therange from 1100° C. to 1300° C.

The term “reductive atmosphere” means an atmosphere having reductiveproperties, preferably an atmosphere of carbon monoxide, forming gas orhydrogen or at least vacuum or an oxygen-deficient atmosphere,preferably in a stream of nitrogen, preferably in a stream of N₂/H₂ andparticularly preferably in a stream of N₂/H₂ (95-80: 5-20).

The term “oxidative atmosphere” has the meaning of an atmosphere havingoxidizing properties, preferably atmosphere of air or oxygen.

Step a) is preferably performed in a micro reactor, a small confinedarea of a flow channel with an internal diameter ranging from 1 mm to 10mm width, wherein two or more solutions are mixed through said flowchannel. In the micro reactor, chemical reactions of the mixed solutionstake place in a confinement with typical lateral dimensions below a fewmillimeters.

The actual composition ratio of the phosphor can be confirmed bywavelength dispersive X-ray spectroscopy (WDX), and the results of WDXcan be used to predetermine the molar ratio of the salt containing theelements Mg, Al, M, A, B and C for the mixing step a).

For the preparation of the mixture in step a), it is possible to preparea mixture of some or all of the salts or components as powders andadding the solvent or to prepare the mixture stepwise directly in asolvent. However, the above-mentioned salts can be added to the mixtureat anytime before the precipitation step (before step b).

The term “silicon containing agent” includes an inorganic siliconcompound, preferably an oxide of silicon having the chemical formulaSiO₂. It has a number of distinct crystalline forms (polymorphs) inaddition to amorphous forms. The SiO₂ should be in small particles witha diameter of less than 1 μm; a diameter of less than 200 nm is evenbetter. The “silicon containing agent” also refers to any organicsilicon compounds, such as tetraalkyl ortho-silicates, alternately knownas tetraalkoxy silanes, preferably tetraethoxysilane ortetramethoxysilane.

Suitable salts of the elements Mg, Al, M, A, B and C are preferablyselected from corresponding nitrates, halogenides, hydrogensulfates orcarbonates, more preferably nitrates or halogenides, and most preferablyof halogenides, in particular chlorides.

The term “solvent” is taken to mean a solvent that does not necessarilydissolve the Si-compound. Water and alcohols, such as methanol, ethanol,etc. are preferred solvents in accordance with the present invention.

Preferred precipitation agents in step b) are preferably selected fromsodium hydrogen carbonate, ammonium chloride, or ammonium hydrogencarbonate, more preferably the precipitation agent is ammonium chloride.

In a preferred embodiment of the invention, the precipitation agents areadded in suitable solvents and preferably mixed with the solvents attemperatures above the melting point of the corresponding solvent andbelow the boiling point of the solvent. More preferably in a temperaturerange up to about 70° C., even more preferably up to about 60° C., andpreferably for at least 1 h or more, more preferably for at least 2hours or more.

In a preferred embodiment of the present invention, a pre-heat treatmentstep can optionally be performed after performing step b) and beforeperforming step c), in order to evaporate the solvent from the mixtureof step b). As commonly known by the expert, suitable temperatureconditions depends mainly on the used solvent. However, preferredtemperature conditions range up to 100° C., more preferably up to 90° C.and even more preferably up to 80° C.

A suitable evaporation atmosphere is not particularly limited to anyparticular conditions regarding pressure or atmosphere. However,preferably, the evaporation of the solvent is performed under an airatmosphere but also applying reduced pressure conditions is applicablein the sense of the present application.

As to step c), an annealing oven, as known to the expert, is preferablydriven under an oxidative atmosphere (such as oxygen or air oroxygen-containing atmosphere). In a further preferred embodiment of theinvention, a commonly known oxidation furnace is used in the step c).

As to step d), an annealing oven, as known to the expert, is preferablydriven under a reductive atmosphere (such as carbon monoxide, purehydrogen, vacuum, or an oxygen-deficient atmosphere). In a furtherpreferred embodiment of the invention, a commonly known reducing furnaceis used in the step d).

The particle size of the phosphors according to the invention istypically between 50 nm and 30 μm, preferably between 1 μm and 20 μm.

In a further preferred embodiment, the phosphors in particle form have acontinuous surface coating consisting of SiO₂, TiO₂, Al₂O₃, ZnO, ZrO₂and/or Y₂O₃ or mixed oxides thereof. This surface coating has theadvantage that, through a suitable grading of the refractive indices ofthe coating materials, the refractive index can be matched to theenvironment. In this case, the scattering of light at the surface of thephosphor is reduced and a greater proportion of the light can penetrateinto the phosphor and be absorbed and converted therein. In addition,the refractive index-matched surface coating enables more light to becoupled out of the phosphor since total internal reflection is reduced.

In addition, a continuous layer is advantageous if the phosphor has tobe encapsulated. This may be necessary in order to counter sensitivityof the phosphor or parts thereof to diffusing water or other materialsin the immediate environment. A further reason for encapsulation with aclosed shell is thermal decoupling of the actual phosphor from the heatgenerated in the chip. This heat results in a reduction in thefluorescence light yield of the phosphor and may also influence thecolour of the fluorescence light.

Finally, a coating of this type enables the efficiency of the phosphorto be increased by preventing lattice vibrations arising in the phosphorfrom propagating to the environment.

In addition, it is preferred for the phosphors to have a porous surfacecoating consisting of SiO₂, TiO₂, Al₂O₃, ZnO, ZrO₂ and/or Y₂O₃ or mixedoxides thereof or of the phosphor composition. These porous coatingsoffer the possibility of further reducing the refractive index of asingle layer. Porous coatings of this type can be produced by threeconventional methods, as described in WO 03/027015, which isincorporated in its full scope into the context of the presentapplication by way of reference: the etching of glass (for examplesoda-lime glasses (see U.S. Pat. No. 4,019,884)), the application of aporous layer, and the combination of a porous layer and an etchingoperation.

In a further preferred embodiment, the phosphor particles have a surfacewhich carries functional groups which facilitate chemical bonding to theenvironment, preferably consisting of epoxy or silicone resin. Thesefunctional groups can be, for example, esters or other derivatives whichare bonded via oxo groups and are able to form links to constituents ofthe binders based on epoxides and/or silicones. Surfaces of this typehave the advantage that homogeneous incorporation of the phosphors intothe binder is facilitated. Furthermore, the rheological properties ofthe phosphor/binder system and also the pot lives can thereby beadjusted to a certain extent. Processing of the mixtures is thussimplified.

Since the phosphor layer according to the invention applied to the LEDchip preferably consists of a mixture of silicone and homogeneousphosphor particles which is applied by bulk casting, and the siliconehas a surface tension, this phosphor layer is not uniform at amicroscopic level or the thickness of the layer is not constantthroughout. This is generally also the case if the phosphor is notapplied by the bulk-casting process, but instead in the so-calledchip-level conversion process, in which a highly concentrated, thinphosphor layer is applied directly to the surface of the chip with theaid of electrostatic methods.

With the aid of the above-mentioned process, it is possible to produceany desired outer shapes of the phosphor particles, such as sphericalparticles, flakes and structured materials and ceramics.

The preparation of flake-form phosphors as a further preferredembodiment is carried out by conventional processes from thecorresponding metal salts and/or rare-earth salts. The preparationprocess is described in detail in EP 763573 and DE 102006054331, whichare incorporated in their full scope into the context of the presentapplication by way of reference. These flake-form phosphors can beprepared by coating a natural or synthetically prepared, highly stablesupport or a substrate comprising, for example, mica, SiO₂, Al₂O₃, ZrO₂,glass or TiO₂ flakes which has a very large aspect ratio, an atomicallysmooth surface and an adjustable thickness with a phosphor layer by aprecipitation reaction in aqueous dispersion or suspension. Besidesmica, ZrO₂, SiO₂, Al₂O₃, glass or TiO₂ or mixtures thereof, the flakesmay also consist of the phosphor material itself or be built up from onematerial. If the flake itself merely serves as support for the phosphorcoating, the latter must consist of a material which is transparent tothe primary radiation of the LED, or absorbs the primary radiation andtransfers this energy to the phosphor layer. The flake-form phosphorsare dispersed in a resin (for example silicone or epoxy resin), and thisdispersion is applied to the LED chip. The flake-form phosphors can beprepared on a large industrial scale in thicknesses of 50 nm to about 20μm, preferably between 150 nm and 5 μm. The diameter here is 50 nm to 20μm.

It generally has an aspect ratio (ratio of the diameter to the particlethickness) of 1:1 to 400:1 and in particular 3:1 to 100:1.

The flake dimensions (length×width) are dependent on the arrangement.Flakes are also suitable as centres of scattering within the conversionlayer, in particular if they have particularly small dimensions.

The surface of the flake-form phosphor according to the invention facingthe LED chip can be provided with a coating which has an antireflectionaction with respect to the primary radiation emitted by the LED chip.This results in a reduction in back-scattering of the primary radiation,enabling the latter to be coupled better into the phosphor bodyaccording to the invention.

Suitable for this purpose are, for example, coatings of matchedrefractive index, which must have a following thickness d: d=[wavelengthof the primary radiation of the LED chip/(4*refractive index of thephosphor ceramic)], see, for example, Gerthsen, Physik [Physics],Springer Verlag, 18th Edition, 1995. This coating may also consist ofphotonic crystals, which also includes structuring of the surface of theflake-form phosphor in order to achieve certain functionalities.

The production of the phosphors according to the invention in the formof ceramic bodies is carried out analogously to the process described inDE 102006037730 (Merck), which is incorporated in its full scope intothe context of the present application by way of reference. In thisprocess, the phosphor is prepared by wet-chemical methods by mixing thecorresponding starting materials and dopants, subsequently subjected toisostatic pressing and applied directly to the surface of the chip inthe form of a homogeneous, thin and non-porous flake. There is thus nolocation-dependent variation of the excitation and emission of thephosphor, which means that the LED provided therewith emits ahomogeneous light cone of constant colour and has high light output. Theceramic phosphor bodies can be produced on a large industrial scale, forexample, as flakes in thicknesses of a few 100 nm to about 500 μm. Theflake dimensions (length×width) are dependent on the arrangement. In thecase of direct application to the chip, the size of the flake should beselected in accordance with the chip dimensions (from about 100 μm*100μm to several mm²) with a certain oversize of about 10% to 30% of thechip surface with a suitable chip arrangement (for example flip-chiparrangement) or correspondingly. If the phosphor flake is installed overa finished LED, the entire exiting light cone passes through the flake.

The side surfaces of the ceramic phosphor body can be coated with alight metal or noble metal, preferably aluminium or silver. The metalcoating has the effect that light does not exit laterally from thephosphor body. Light exiting laterally can reduce the luminous flux tobe coupled out of the LED. The metal coating of the ceramic phosphorbody is carried out in a process step after the isostatic pressing togive rods or flakes, where the rods or flakes can optionally be cut tothe requisite size before the metal coating. To this end, the sidesurfaces are wetted, for example, with a solution comprising silvernitrate and glucose and subsequently exposed to an ammonia atmosphere atelevated temperature. A silver coating, for example, forms on the sidesurfaces in the process.

Alternatively, current less metallisation processes are also suitable,see, for example, Hollemann-Wiberg, Lehrbuch der Anorganischen Chemie[Textbook of Inorganic Chemistry], Walter de Gruyter Verlag or UllmannsEnzyklopädie der chemischen Technologie [Ullmann's Encyclopaedia ofChemical Technology].

The ceramic phosphor body can, if necessary, be fixed to the baseboardof an LED chip using a water-glass solution.

In a further embodiment, the ceramic phosphor body has a structured (forexample pyramidal) surface on the side opposite an LED chip. Thisenables as much light as possible to be coupled out of the phosphorbody. The structured surface on the phosphor body is produced bycarrying out the isostatic pressing using a compression mould having astructured pressure plate and thus embossing a structure into thesurface. Structured surfaces are desired if the aim is to produce thethinnest possible phosphor bodies or flakes. The pressing conditions areknown to the person skilled in the art (see J. Kriegsmann, Technischekeramische Werkstoffe [Industrial Ceramic Materials], Chapter 4,Deutscher Wirtschaftsdienst, 1998). It is important that the pressingtemperatures used are ⅔ to ⅚ of the melting point of the substance to bepressed.

The compounds according to the present invention exhibit high thermalquenching resistivity.

The term “thermal quenching resistivity” means an emission intensitydecrease at higher temperature compared to an original intensity at 25°C.

The compounds according to the present invention exhibit an highchemical stability against humidity or moisture with regards todecomposition.

The compounds according to the present invention preferably exhibit aquantum efficiency of at least 80% and more preferably of at least 90%.

The compounds of the present invention are of good LED quality. In thecontext of this application, the LED quality is determined by commonlyknown parameters, such as the color rendering index (CRI), theCorrelated Color Temperature (CCT), the lumen equivalent or absolutelumen, and the color point in CIE x and y coordinates.

The Color Rendering Index (CRI), as known to the expert, is a unit lessphotometric size, which compares the color fidelity of an artificiallight source to that of sunlight or filament light sources (the lattertwo have a CRI of 100).

The Correlated Color Temperature (CCT), as known to the expert, is aphotometric variable having the unit Kelvin. The higher the number, thegreater the blue component of the light and the colder the white lightof an artificial light source appears to the viewer. The CCT follows theconcept of the black light blue lamp, which color temperature describesthe so-called Planck's curve in the CIE diagram.

The lumen equivalent, as known to the expert, is a photometric variablehaving the unit the lm/W. The lumen equivalent describes the size of thephotometric luminous flux of a light source at a specific radiometricradiation power having the unit is watts. The higher the lumenequivalent is, the more efficient is a light source.

The lumen, as known to the expert, is photometric variable, whichdescribes the luminous flux of a light source, which is a measure of thetotal radiation emitted by a light source in the VIS region. The greaterthe light output, the brighter the light source appears to the observer.

CIE x and CIE y are the coordinates of the CIE chromaticity diagram(here 1931 standard observer), which describes the color of a lightsource.

All of the above variables can be calculated from the emission spectraof the light source by methods known to the expert.

The phosphors according to the present invention can be used as obtainedor in a mixture with other phosphors. Therefore, the present inventionalso relates phosphor mixtures comprising at least one compoundaccording to the present invention.

Suitable phosphors for a mixture according to the present invention arefor example:

Ba₂SiO₄:Eu²⁺, BaSi₂O₅:Pb²⁺, Ba_(x)Sr_(1-x)F₂:Eu²⁺, BaSrMgSi₂O₇:Eu²⁺,BaTiP₂O₇, (Ba,Ti)₂P₂O₇:Ti, Ba₃WO₆:U, BaY₂F₈:Er³⁺, Yb⁺, Be₂SiO₄:Mn²⁺,Bi₄Ge₃O₁₂, CaAl₂O₄:Ce³⁺, CaLa₄O₇:Ce³⁺, CaAl₂O₄:Eu²⁺, CaAl₂O₄:Mn²⁺,CaAl₄O₇: Pb²⁺, Mn², CaAl₂O₄:Tb³⁺, Ca₃Al₂Si₃O₁₂:Ce³⁺, Ca₃Al₂Si₃O₁₂:Ce³⁺,Ca₃Al₂Si₃O₁₂:Eu²⁺, Ca₂B₅O₉Br:Eu²⁺Ca₂B₅O₉Cl:Eu²⁺, Ca₂B₅O₉Cl:Pb²⁺,CaB₂O₄:Mn²⁺, Ca₂B₂O₅:Mn²⁺CaB₂O₄:Pb²⁺, CaB₂P₂O₉:Eu²⁺, Ca₅B₂SiO₁₀:Eu³⁺,Ca_(0.5)Ba_(0.5)Al₁₂O₁₉:Ce³⁺, Mn²⁺, Ca₂Ba₃(PO₄)₃Cl:Eu²⁺, CaBr₂:Eu² inSiO₂, CaCl₂:Eu² in SiO₂, CaCl₂:Eu²⁺, Mn² in SiO₂, CaF₂:Ce³⁺, CaF₂:Ce³⁺,Mn²⁺, CaF₂:Ce³⁺, Tb³⁺, CaF₂:Eu²⁺, CaF₂:Mn²⁺, CaF₂:U, CaGa₂O₄:Mn²⁺,CaGa₄O₇:Mn²⁺, CaGa₂S₄:Ce³⁺, CaGa₂S₄:Eu²⁺, CaGa₂S₄:Mn²⁺, CaGa₂S₄:Pb²⁺,CaGeO₃:Mn²⁺, CaI₂:Eu² in SiO₂, CaI₂:Eu²⁺, Mn²⁺ in SiO₂, CaLaBO₄:Eu³⁺,CaLaB₃O₇:Ce³⁺, Mn²⁺, Ca₂La₂BO_(6.5):Pb²⁺, Ca₂MgSi₂O₇, Ca₂MgSi₂O₇:Ce³⁺,CaMgSi₂O₆:Eu²⁺, Ca₃MgSi₂O₈:Eu²⁺, Ca₂MgSi₂O₇:Eu²⁺, CaMgSi₂O₆:Eu²⁺, Mn²⁺,Ca₂MgSi₂O₇:Eu²⁺, Mn²⁺, CaMoO₄, CaMoO₄:Eu³⁺, CaO:Bi³⁺, CaO:Cd²⁺, CaO:Cu⁺,CaO:Eu³⁺, CaO:Eu³⁺, Na⁺, CaO:Mn²⁺, CaO:Pb²⁺, CaO:Sb³⁺, CaO:Sm³⁺,CaO:Tb³⁺, CaO:Tl, CaO:Zn²⁺, Ca₂P₂O₇:Ce³⁺, α-Ca₃(PO₄)₂:Ce³⁺,β-Ca₃(PO₄)₂:Ce³⁺, Ca₅(PO₄)₃Cl:Eu²⁺, Ca₅(PO₄)₃Cl:Mn²⁺, Ca₅(PO₄)₃Cl:Sb³⁺,Ca₅(PO₄)₃Cl:Sn²⁺, β-Ca₃(PO₄)₂:Eu²⁺, Mn²⁺, Ca₅(PO₄)₃F:Mn²⁺,Ca_(s)(PO₄)₃F:Sb³⁺, Ca_(s)(PO₄)₃F:Sn²⁺, α-Ca₃(PO₄)₂:Eu²⁺,β-Ca₃(PO₄)₂:Eu²⁺, Ca₂P₂O₇:Eu²⁺, Ca₂P₂O₇:Eu²⁺, Mn²⁺, CaP₂O₆:Mn²⁺,α-Ca₃(PO₄)₂:Pb²⁺, α-Ca₃(PO₄)₂:Sn²⁺, β-Ca₃(PO₄)₂:Sn²⁺, β-Ca₂P₂O₇:Sn, Mn,α-Ca₃(PO₄)₂:Tr, CaS:Bi³⁺, CaS:Bi³⁺, Na, CaS:Ce³⁺, CaS:Eu²⁺, CaS:Cu⁺,Na⁺, CaS:La³⁺, CaS:Mn²⁺, CaSO₄:Bi, CaSO₄:Ce³⁺, CaSO₄:Ce³⁺, Mn²⁺,CaSO₄:Eu²⁺, CaSO₄:Eu²⁺, Mn²⁺, CaSO₄:Pb²⁺, CaS:Pb²⁺, CaS:Pb²⁺, Cl,CaS:Pb²⁺, Mn²⁺, CaS:Pr³⁺, Pb²⁺, Cl, CaS:Sb³⁺, CaS:Sb³⁺, Na, CaS:Sm³⁺,CaS:Sn²⁺, CaS:Sn²⁺, F, CaS:Tb³⁺, CaS:Tb³⁺, Cl, CaS:Y³⁺, CaS:Yb²⁺,CaS:Yb²⁺, Cl, CaSiO₃:Ce³⁺, Ca₃SiO₄Cl₂:Eu²⁺, Ca₃SiO₄Cl₂:Pb²⁺,CaSiO₃:Eu²⁺, CaSiO₃:Mn²⁺, Pb, CaSiO₃:Pb²⁺, CaSiO₃:Pb²⁺, Mn²⁺,CaSiO₃:Ti⁴⁺, CaSr₂(PO₄)₂:Bi³⁺, β-(Ca, Sr)₃(PO₄)₂:Sn²⁺Mn²⁺,CaTi_(0.9)Al_(0.1)O₃:Bi³⁺, CaTiO₃:Eu³⁺, CaTiO₃:Pr³⁺, Ca₅(VO₄)₃Cl, CaWO₄,CaWO₄:Pb²⁺, CaWO₄:W, Ca₃WO₆:U, CaYAlO₄:Eu³⁺, CaYBO₄:Bi³⁺, CaYBO₄:Eu³⁺,CaYB_(0.8)O_(3.7):Eu³⁺, CaY₂ZrO₆:Eu³⁺, (Ca, Zn, Mg)₃(PO₄)₂:Sn, CeF₃,(Ce, Mg)BaAl₁₁O₁₈:Ce, (Ce, Mg)SrAl₁₁O₁₈:Ce, CeMgAl₁₁O₁₉:Ce:Tb,Cd₂B₆O₁₁:Mn²⁺, CdS:Ag⁺, Cr, CdS:In, CdS:In, CdS:In, Te, CdS:Te, CdWO₄,CsF, CsI, CsI:Na⁺, CsI:Tl, (ErCl₃)_(0.25)(BaCl₂)_(0.75), GaN:Zn,Gd₃Ga₅O₁₂:Cr³⁺, Gd₃Ga₅O₁₂:Cr, Ce, GdNbO₄:Bi³⁺, Gd₂O₂S:Eu³⁺, Gd₂O₂Pr³⁺,Gd₂O₂S:Pr, Ce, F, Gd₂O₂S:Tb³⁺, Gd₂SiO₅:Ce³⁺, KAl₁₁O₁₇:Tl⁺,KGa₁₁O₁₇:Mn²⁺, K₂La₂Ti₃O₁₀:Eu, KMgF₃:Eu²⁺, KMgF₃:Mn²⁺, K₂SiF₆:Mn⁴⁺,LaAl₃B₄O₁₂:Eu³⁺, LaAlB₂O₆:Eu³⁺, LaAlO₃:Eu³⁺, LaAlO₃:Sm³⁺, LaAsO₄:Eu³⁺,LaBr₃:Ce³⁺, LaBO₃:Eu³⁺, (La, Ce, Tb) PO₄:Ce:Tb, LaCl₃:Ce³⁺, La₂O₃:Bi³⁺,LaOBr:Tb³⁺, LaOBr:Tm³⁺, LaOCl:Bi³⁺, LaOCl:Eu³⁺, LaOF:Eu³⁺, La₂O₃:Eu³⁺,La₂O₃:Pr³⁺, La₂O₂S:Tb³⁺, LaPO₄:Ce³⁺, LaPO₄:Eu³⁺, LaSiO₃Cl:Ce³⁺,LaSiO₃Cl:Ce³⁺, Tb³⁺, LaVO₄:Eu³⁺, La₂W₃O₁₂:Eu³⁺, LiAlF₄:Mn²⁺,LiAl₅O₈:Fe³⁺, LiAlO₂:Fe³⁺, LiAlO₂:Mn²⁺, LiAl₅O₈:Mn²⁺, Li₂CaP₂O₇:Ce³⁺,Mn²⁺, LiCeBa₄Si₄O₁₄:Mn²⁺, LiCeSrBa₃Si₄O₁₄:Mn²⁺, LiInO₂:Eu³⁺,LiInO₂:Sm³⁺, LiLaO₂:Eu³⁺, LuAlO₃:Ce³⁺, (Lu, Gd)₂SiO₅:Ce³⁺, Lu₂SiO₅:Ce³⁺,Lu₂Si₂O₇:Ce³⁺, LuTaO₄:Nb⁵⁺, Lu_(1-x)Y_(x)AlO₃:Ce³⁺, MgAl₂O₄:Mn²⁺,MgSrAl₁₀O₁₇:Ce, MgB₂O₄:Mn²⁺, MgBa₂(PO₄)₂:Sn²⁺, MgBa₂(PO₄)₂:U,MgBaP₂O₇:Eu²⁺, MgBaP₂O₇:Eu²⁺, Mn²⁺, MgBa₃Si₂O₈:Eu²⁺, MgBa(SO₄)₂:Eu²⁺,Mg₃Ca₃(PO₄)₄:Eu²⁺, MgCaP₂O₇:Mn²⁺, Mg₂Ca(SO₄)₃:Eu²⁺, Mg₂Ca(SO₄)₃:Eu²⁺,Mn², MgCeAl_(n)O₁₉:Tb³⁺, Mg₄(F)GeO₆:Mn²⁺, Mg₄(F)(Ge, Sn)O₆:Mn²⁺,MgF₂:Mn²⁺, MgGa₂O₄:Mn²⁺, Mg₈Ge₂O₁₁F₂:Mn⁴⁺, MgS:Eu²⁺, MgSiO₃:Mn²⁺,Mg₂SiO₄:Mn²⁺, Mg₃SiO₃F₄:Ti⁴⁺, MgSO₄:Eu²⁺MgSO₄:Pb²⁺, MgSrBa₂Si₂O₇:Eu²⁺,MgSrP₂O₇:Eu²⁺, MgSr₅(PO₄)₄:Sn²⁺, MgSr₃Si₂O₈:Eu²⁺, Mn²⁺,Mg₂Sr(SO₄)₃:Eu²⁺, Mg₂TiO₄:Mn⁴⁺, MgWO₄, MgYBO₄:Eu³⁺, Na₃Ce(PO₄)₂:Tb³⁺,NaI:Tl, Na₁₋₂₃K_(O-42)Eu₀₋₁₂TiSi₄O₁₁:Eu³⁺,Na_(1.23)K_(0.42)Eu_(0.12)TiSi₅O₁₃.xH₂O:Eu³⁺,Na_(1.29)K_(0.46)Er_(0.08)TiSi₄O₁₁:Eu³⁺, Na₂Mg₃Al₂Si₂O₁₀:Tb,Na(Mg_(2-x)Mn_(x))LiSi₄O₁₀F₂:Mn, NaYF₄:Er³⁺, Yb³⁺, NaYO₂:Eu³⁺,SrAl₁₂O₁₉:Ce³⁺, Mn²⁺, SrAl₂O₄:Eu²⁺, SrAl₄O₇:Eu³⁺, SrAl₁₂O₁₉:Eu²⁺,SrAl₂S₄:Eu²⁺, Sr₂B₅O₉Cl:Eu²⁺, SrB₄O₇:Eu²⁺(F, Cl, Br), SrB₄O₇:Pb²⁺,SrB₄O₇:Pb²⁺, Mn²⁺, SrB₈O₁₃:Sm²⁺, Sr_(x)Ba_(y)Cl_(z)Al₂O_(4-z/2): Mn²⁺,Ce³⁺, SrBaSiO₄:Eu²⁺, Sr(Cl, Br, I)₂:Eu²⁺ in SiO₂, SrCl₂:Eu²⁺ in SiO₂,Sr₅Cl(PO₄)₃:Eu, Sr_(w)F_(x)B₄O_(6.5):Eu²⁺, Sr_(w)F_(x)B_(y)O_(z):Eu²⁺,Sm²⁺, SrF₂:Eu²⁺, SrGa₁₂O₁₉:Mn²⁺, SrGa₂S₄:Ce³⁺, SrGa₂S₄:Eu²⁺,SrGa₂S₄:Pb²⁺, SrIn₂O₄:Pr³⁺, Al³⁺, (Sr, Mg)₃(PO₄)₂:Sn, SrMgSi₂O₆:Eu²⁺,Sr₂MgSi₂O₇:Eu²⁺, Sr₃MgSi₂O₈:Eu²⁺, SrMoO₄:U, SrO.3B₂O₃:Eu²⁺, Cl,ß-SrO.3B₂O₃:Pb²⁺, ß-SrO.3B₂O₃:Pb²⁺, Mn²⁺, α-SrO.3B₂O₃:Sm²⁺,Sr₆P₅BO₂₀:Eu, Sr₅(PO₄)₃Cl:Eu²⁺, Sr₅(PO₄)₃Cl:Eu²⁺, Pr³⁺, Sr₅(PO₄₃Cl:Mn²⁺,Sr₅(PO₄)₃Cl:Sb³⁺, Sr₂P₂O₇:Eu²⁺, β-Sr₃(PO₄)₂:Eu²⁺, Sr₅(PO₄)₃F:Mn²⁺,Sr₅(PO₄)₃F:Sb³⁺, Sr₅(PO₄)₃F:Sb³⁺, Mn²⁺, Sr₅(PO₄)₃F:Sn²⁺, Sr₂P₂O₇:Sn²⁺,β-Sr₃(PO₄)₂:Sn²⁺, β-Sr₃(PO₄)₂:Sn²⁺, Mn²⁺(Al), SrS:Ce³⁺, SrS:Eu²⁺,SrS:Mn²⁺, SrS:Cu⁺, Na, SrSO₄:Bi, SrSO₄:Ce³⁺, SrSO₄:Eu²⁺, SrSO₄:Eu²⁺,Mn²⁺, Sr₅Si₄O₁₀Cl₆:Eu²⁺, Sr₂SiO₄:Eu²⁺, SrTiO₃:Pr³⁺, SrTiO₃:Pr³⁺, Al³⁺,Sr₃WO₆:U, SrY₂O₃:Eu³⁺, ThO₂:Eu³⁺, ThO₂:Pr³⁺, ThO₂:Tb³⁺, YAl₃B₄O₁₂:Bi³⁺,YAl₃B₄O₁₂:Ce³⁺, YAl₃B₄O₁₂:Ce³⁺, Mn, YAl₃B₄O₁₂:Ce³⁺, Tb³⁺,YAl₃B₄O₁₂:Eu³⁺, YAl₃B₄O₁₂:Eu³⁺, Cr³⁺, YAl₃B₄O₁₂:Th⁴⁺, Ce³⁺, Mn²⁺,YAlO₃:Ce³⁺, Y₃Al₅O₁₂:Ce³⁺, Y₃Al₅O₁₂:Cr³⁺, YAlO₃:Eu³⁺, Y₃Al₅O₁₂:Eu³⁺,Y₄Al₂O₉:Eu³⁺, Y₃Al₅O₁₂:Mn⁴⁺, YAlO₃:Sm³⁺, YAlO₃:Tb³⁺, Y₃Al₅O₁₂:Tb³⁺,YAsO₄:Eu³⁺, YBO₃:Ce³⁺, YBO₃:Eu³⁺, YF₃:Er³⁺, Yb³⁺, YF₃:Mn²⁺, YF₃:Mn²⁺,Th⁴⁺, YF₃:Tm³⁺, Yb³⁺, (Y, Gd)BO₃:Eu, (Y, Gd)BO₃:Tb, (Y, Gd)₂O₃:Eu³⁺,Y_(1.34)Gd_(0.603)(Eu, Pr), Y₂O₃:Bi³⁺, YOBr:Eu³⁺, Y₂O₃:Ce, Y₂O₃:Er³⁺,Y₂O₃:Eu³⁺(YOE), Y₂O₃:Ce³⁺, Tb³⁺, YOCl:Ce³⁺, YOCl:Eu³⁺, YOF:Eu³⁺,YOF:Tb³⁺, Y₂O₃:Ho³⁺, Y₂O₂S:Eu³⁺, Y₂O₂S:Pr³⁺, Y₂O₂S:Tb³⁺, Y₂O₃:Tb³⁺,YPO₄:Ce³⁺, YPO₄:Ce³⁺, Tb³⁺, YPO₄:Eu³⁺, YPO₄:Mn²⁺, Th⁴⁺, YPO₄:V⁵⁺,Y(P,V)O₄:Eu, Y₂SiO₅:Ce³⁺, YTaO₄, YTaO₄:Nb⁵⁺, YVO₄:Dy³⁺, YVO₄:Eu³⁺,ZnAl₂O₄:Mn²⁺, ZnB₂O₄:Mn²⁺, ZnBa₂S₃:Mn²⁺, (Zn, Be)₂SiO₄:Mn²⁺,Zn_(0.4)Cd_(0.6)S:Ag, Zn_(0.6)Cd_(0.4)S:Ag, (Zn, Cd)S:Ag, Cl, (Zn,Cd)S:Cu, ZnF₂:Mn²⁺, ZnGa₂O₄, ZnGa₂O₄:Mn²⁺, ZnGa₂S₄:Mn²⁺, Zn₂GeO₄:Mn²⁺,(Zn, Mg)F₂:Mn²⁺, ZnMg₂(PO₄)₂:Mn²⁺, (Zn, Mg)₃(PO₄)₂:Mn²⁺, ZnO:Al³⁺, Ga³⁺,ZnO:Bi³⁺, ZnO:Ga³⁺, ZnO:Ga, ZnO—CdO:Ga, ZnO:S, ZnO:Se, ZnO:Zn, ZnS:Ag⁺,Cl⁻, ZnS:Ag, Cu, Cl, ZnS:Ag, Ni, ZnS:Au, In, ZnS—CdS (25-75), ZnS—CdS(50-50), ZnS—CdS (75-25), ZnS—CdS:Ag, Br, Ni, ZnS—CdS:Ag⁺, Cl,ZnS—CdS:Cu, Br, ZnS—CdS:Cu, I, ZnS:Cl⁻, ZnS:Eu²⁺, ZnS:Cu, ZnS:Cu⁺, Al³⁺,ZnS:Cu⁺, Cl⁻, ZnS:Cu, Sn, ZnS:Eu²⁺, ZnS:Mn²⁺, ZnS:Mn, Cu, ZnS:Mn²⁺,Te²⁺, ZnS:P, ZnS:P³⁻, Cl⁻, ZnS:Pb²⁺, ZnS:Pb²⁺, Cl⁻, ZnS:Pb, Cu,Zn₃(PO₄)₂:Mn²⁺, Zn₂SiO₄:Mn²⁺, Zn₂SiO₄:Mn²⁺, As⁵⁺, Zn₂SiO₄:Mn, Sb₂O₂,Zn₂SiO₄:Mn²⁺, P, Zn₂SiO₄:Ti⁴⁺, ZnS:Sn²⁺, ZnS:Sn, Ag, ZnS:Sn²⁺, Li⁺,ZnS:Te, Mn, ZnS—ZnTe:Mn²⁺, ZnSe:Cu⁺, Cl and ZnWO₄.

As mentioned above, the phosphors according to the present invention canbe excited over a broad range, extending from about 280 nm to 400 nm,preferably 300 nm to about 400 nm.

Accordingly, the present invention also relates to the use of at leastone compound according to the present invention as a conversion phosphorfor the conversion of all or some of the UV or near-UV radiation emittedby an suitable light source.

Thus, the present invention also relates to an illumination unit, whichcomprises at least one light source with an emission maximum in therange of 280 nm to 400 nm, and all or some of this radiation isconverted into longer-wavelength radiation by a compound according tothe present invention or a corresponding phosphor mixture as describedabove and below.

Preferably, the illumination unit comprises an UV or near UV LED and atleast one phosphor according to the present invention. Such illuminationunit is preferably white-light-emitting, in particular having a colourcoordinate of x=0.12-0.43 and y=0.07-0.43, more preferably x=0.15-0.33and y=0.10-0.33,

Preference is furthermore given to an illumination unit, in particularfor general lighting, which is characterised in that it has a CRI >60,preferably >70, more preferably >80.

In another embodiment, the illumination unit emits light having acertain colour point (colour-on-demand principle). The colour-on-demandconcept is taken to mean the production of light having a certain colourpoint using a pcLED (=phosphor-converted LED) using one or morephosphors. This concept is used, for example, in order to producecertain corporate designs, for example for illuminated company logos,trademarks, etc.

Especially for the purpose that certain colour spaces should beestablished, the phosphor is preferably mixed with at least one furtherphosphor selected from the group of oxides, molybdates, tungstates,vanadates, garnets, silicates, aluminates, nitrides and oxynitrides, ineach case individually or mixtures thereof with one or more activatorions, such as Ce, Eu, Mn, Cr and/or Bi.

Suitable green emitting phosphors, are preferably selected from Ce-dopedlutetium-containing garnets, Eu-doped sulfoselenides, thiogallates,BaMgAl₁₀O₁₇:EuMn (BAM:EuMn), SrGa₂S₄:Eu and/or Ce- and/or Eu-dopednitride containing phosphors and/or β-SiAlON:Eu.

Suitable blue-emitting phosphor, are preferably selected from BAM: Eu orSr₁₀(PO₄)₆Cl₂:Eu.

Suitable phosphors emitting yellow light, can preferably selected fromgarnet phosphors (e.g., (YTbGd)₃Al₅O₁₂:Ce), ortho-silicates phosphors(e.g., (CaSrBa)₂SiO₄: Eu), or Sialon-phosphors (e.g., α-SiAlON: Eu).

The term “blue-emitting phosphor” refers to a phosphor emitting awavelength having at least one emission maximum between 435 nm and 507nm.

The term “green emitting phosphor” refers to a phosphor emitting awavelength having at least one emission maximum between 508 nm and 550nm.

The term “yellow emitting phosphor” or refers to a phosphor emitting awavelength having at least one emission maximum between 551 nm and 585nm.

The term “red-emitting phosphor” refers to a phosphor emitting awavelength having at least one emission maximum between 586 and 670 nm.

In a preferred embodiment, the illumination unit according to theinvention comprises a light source, which is a luminescent indiumaluminium gallium nitride, in particular of the formulaIn_(i)Ga_(j)Al_(k)N, where 0≤i,0≤j,0≤k, and i+j+k=1.

In a another preferred embodiment of the illumination unit according tothe invention, the light source is a luminescent arrangement based onZnO, TCO (transparent conducting oxide), ZnSe or SiC or an arrangementbased on an organic light-emitting layer (OLED).

In a further preferred embodiment of the illumination unit according tothe invention, the light source is a source which exhibitselectroluminescence and/or photoluminescence. The light source mayfurthermore also be a plasma or discharge source. Possible forms oflight sources of this type are known to the person skilled in the art.These can be light-emitting LED chips of various structures.

The phosphors according to the invention can either be dispersed in aresin (for example epoxy or silicone resin) or, in the case of suitablesize ratios, arranged directly on the light source or alternativelyarranged remote there from, depending on the application (the latterarrangement also includes “remote phosphor technology”). The advantagesof remote phosphor technology are known to the person skilled in the artand are revealed, for example, by the following publication: JapaneseJournal of Appl. Phys. Vol. 44, No. 21 (2005). L649-L651.

Compounds according to the present invention are also suitable forconverting parts of solar irradiation radiation having a wavelength ofless than approximately 400 nm into radiation of a wavelength of morethan approximately 400 nm, which can be utilized more effectively by avariety of semiconductor materials in solar cells.

Therefore, the present invention also relates to the use of at least onecompound according to the invention as a wavelength conversion materialfor solar cells.

Thus, the invention relates also to a method of improvement of a solarcell module by applying e.g. a polymer film comprising a phosphoraccording to the present invention, which is capable to increase thelight utilization efficiency and the power-generating efficiency, due toa wavelength conversion of the shortwave part of the solar irradiationspectrum which normally cannot be utilized due to the absorptioncharacteristics of the semiconductor material in the solar cell module.

The present invention is described above and below with particularreference to the preferred embodiments. It should be understood thatvarious changes and modifications might be made therein, withoutdeparting from the spirit and scope of the invention.

Many of the compounds or mixtures thereof, mentioned above and below,are commercially available. The organic compounds are either known orcan be prepared by methods which are known per se, as described in theliterature (for example in the standard works such as Houben-Weyl,Methoden der Organischen Chemie [Methods of Organic Chemistry],Georg-Thieme-Verlag, Stuttgart), to be precise under reaction conditionswhich are known and suitable for said reactions. Use may also be madehere of variants which are known per se, but are not mentioned here.

Unless the context clearly indicates otherwise, as used herein pluralforms of the terms herein are to be construed as including the singularform and vice versa.

Throughout this application, unless explicitly stated otherwise, allconcentrations are given in weight percent and relate to the respectivecomplete mixture, all temperatures are given in degrees centigrade(Celsius) and all differences of temperatures in degrees centigrade.

Throughout the description and claims of this specification, the words“comprise” and “contain” and variations of the words, for example“comprising” and “comprises”, mean “including but not limited to”, andare not intended to (and do not) exclude other components. On the otherhand, the word “comprise” also encompasses the term “consisting of” butis not limited to it.

It will be appreciated that variations to the foregoing embodiments ofthe invention can be made while still falling within the scope of theinvention. Each feature disclosed in this specification, unless statedotherwise, may be replaced by alternative features serving the same,equivalent, or similar purpose. Thus, unless stated otherwise, eachfeature disclosed is only one example of a generic series of equivalentor similar features.

All of the features disclosed in this specification may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. In particular, thepreferred features of the invention are applicable to all aspects of theinvention and may be used in any combination. Likewise, featuresdescribed in non-essential combinations may be used separately (not incombination).

It will be appreciated that many of the features described above,particularly of the preferred embodiments, are inventive in their ownright and not just as part of an embodiment of the present invention.

Independent protection may be sought for these features in addition to,or alternative to any invention presently claimed.

The invention will now be described in more detail by reference to thefollowing examples, which are illustrative only and do not limit thescope of the invention.

EXAMPLES Example 1 Preparation of(Ca_(0.8))(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆: Mn²⁺ _(0.2)Eu²⁺_(0.2) Via the Co-Precipitation Method

AlCl₃x6H₂O (0.0075 mol, Merck), CaCl₂x2H₂O (0.0200 mol, Merck), SiO₂(0.0463 mol, Merck), EuCl₃x6H₂O (0.0050 mol, Auer-Remy), MnCl₂x4H₂O(0.0050 mol, Merck), and MgCl₂ x4H₂O (0.0163 mol, Merck) are dissolvedin deionised water. NH₄HCO₃ (0.5 mol, Merck) is dissolved separately indeionised water. The two aqueous solutions are simultaneously stirredinto deionised water. The combined solution is heated to 90° C. andevaporated to dryness. The residue is annealed at 1000° C. for 4 hoursunder an oxidative atmosphere. The resulting oxide material is annealedat 1000° C. for 4 hours under a reductive atmosphere. After conventionalpurification steps (washing with water and drying), the desired(Ca_(0.8)Eu_(0.2)) (Mg_(0.65)Mn_(0.2)Al_(0.15))(Si_(1.85)Al_(0.15))O₆ ischaracterized by the XRD (cf. FIG. 1).

The composition ratio of the phosphor (Al/Si ratio) is confirmed by WDX.The phosphor emits a bright red light having two main peaks at 435 and585 nm upon excitation at 350 nm (cf. FIG. 2).

The emission intensity of 680 nm (which has low spectral sensitivity tothe human eye) decreased upon the addition of Al to the CaMgSi₂O₆:EuMnphosphor.

Example 2 Preparation of(Ca_(0.8))(Mg_(0.5)Al_(0.3))(Si_(0.7)Al_(0.3))O₆: Mn²⁺ _(0.2)Eu²⁺ _(0.2)Via the Co-Precipitation Method

AlCl₃x6H₂O (0.0150 mol, Merck), CaCl₂x2H₂O (0.0200 mol, Merck), SiO₂(0.0425 mol, Merck), EuCl₃x6H₂O (0.0050 mol, Auer-Remy), MnCl₂x4H₂O(0.0050 mol, Merck), and MgCl₂ x4H₂O (0.0125 mol, Merck) are dissolvedin deionised water. NH₄HCO₃ (0.5 mol, Merck) is dissolved separately indeionised water. The two aqueous solutions are then simultaneouslystirred into deionised water. The resulting solution is heated to 90° C.and evaporated to dryness. The remaining solid is annealed at 1000° C.for 4 hours under an oxidative atmosphere. The resultant oxide materialsare annealed at 1000° C. for 4 hours under a reductive atmosphere. Afterperforming conventional purification steps using water and drying,(Ca_(0.8)) (Mg_(0.5)Al_(0.3))(Si_(1.7)Al_(0.3))O₆: Mn²⁺ _(0.2)Eu²⁺_(0.2) is obtained and characterized by XRD techniques (FIG. 3).

The composition ratio of the phosphor (Al/Si ratio) is confirmed by WDX.The phosphor emits upon excitation with light of 350 nm a bright redlight with two emission peaks centred at 435 and 585 nm (FIG. 4).

The emission intensity at a wavelength of 680 nm (which has a lowspectral sensitivity to the human eye) decreased upon addition of Al tothe CaMgSi₂O₆:EuMn phosphor.

Example 3 Preparation of(Ca_(0.64)Sr_(0.16))(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆: Mn²⁺_(0.2)Eu²⁺ _(0.2) Via the Micro Reaction Method

The influence of the product has been investigated by changing the tubediameter and flow rate. Tube diameter influences activatorsdistribution, and flow rate influences the crystalline. AlCl₃x6H₂O(0.0075 mol, Merck), CaCl₂x2H₂O (0.0160 mol, Merck), SrCl₂x2H₂O (0.0040mol, Merck), SiO₂ (0.0463 mol, Merck), EuCl₃x6H₂O (0.0050 mol,Auer-Remy), MnCl₂x4H₂O (0.0050 mol, Merck), and MgCl₂ x4H₂O (0.0125 mol,Merck) are dissolved together in deionised water. Then, NH₄HCO₃ (0.5mol, Merck) is dissolved separately in deionised water. The solutionsare pumped at the same time and driven a reaction at the connector. Thereaction solution is passed through the tube at about 60° C. Precursorsare caught in a beaker. The resultant solution is evaporated to drynessat about 90° C., and the resultant solid is annealed at 1000° C. for 4hours in the oxidation atmosphere. The resultant oxide materials areannealed at 1000° C. for 4 hours in the reduction atmosphere. Afterconventional purification steps using water and drying are performed,the desired (Ca_(0.64)Sr_(0.16))(Mg_(0.65)Al_(0.15))(Si_(1.85)Al_(0.15))O₆: Mn²⁺ _(0.2)Eu²⁺ _(0.2) isformed as evidenced by XRD pattern (cf. FIG. 5). The composition ratioof the phosphor (Al/Si ratio) was confirmed by WDX. The phosphor emits abright red light peaking at 435 and 585 nm upon 350 nm light excitation(FIG. 6).

The emission intensity at a wavelength of 680 nm (which has a lowspectral sensitivity to the human eye) decreased upon addition of Al tothe CaMgSi₂O₆:EuMn phosphor.

Example 4 White LED with a 380 nm-Emitting LED Chip Using(Ca_(0.8)Eu_(0.2)) (Mg_(0.5)Mn_(0.2)Al_(0.3))(Si_(1.7)Al_(0.3))O₆Phosphor

The phosphor from Example 2,(Ca_(0.8))(Mg_(0.5)Al_(0.3))(Si_(1.7)Al_(0.3))O₆: Mn²⁺ _(0.2)Eu²⁺ _(0.2)is mixed in a tumble mixer with a silicone resin system OE 6550 (DowCorning). The final concentration of phosphor in the silicone is 8molpercentage. The slurry is applied to an InGaN-based LED chip emittinga wavelength of 380 nm.

The resulting illumination unit emits light with white colour, CIE 1937(x, y)=(0.28, 0.31).

Example 5

Measurement of Thermal Quenching

The phosphor of Example 1 is placed in a sample holder.

The holder is placed to an FP6500 (JASCO) under a thermal controller(JASCO) which serves as its TQ measurement system.

The intensity of the emission spectra of the phosphor, which ranges from380 nm to 780 nm is measured by the FP6500 in dependence of theincreasing temperature starting at 25° C. and increased by increments of25° C. up to 100° C.

A 150 W xenon lamp with an excitation wavelength of 350 nm is used asthe excitation light source.

A comparative phosphor having the formula CaMgSi2O6: Eu²⁺Mn²⁺ is placedin the sample holder and the experiment is performed in the same manneras the phosphor from Example 1.

As a result, the integrated emission intensity of the phosphor ofExample 1 is 5% higher than the integrated emission intensity of thecomparative example (cf. FIG. 8). This result clearly shows the efficacyof the thermal quenching resistivity of phosphors according to thepresent invention.

The invention claimed is:
 1. A compound of formula Ia(M_(1-x-u-p))(Mg_(1-z-v-q)Al_(z-m))(Si_(2-z)T_(z-n))O₆:A_(x)B_(y)C_(w)  Iawherein M denotes at least one alkaline earth element selected from thegroup consisting of Ca, Sr, and Ba, T denotes at least one trivalentelement selected from the group consisting of Al, Ga, In, and Sc, A andB denote differently from each other, a divalent element selected fromthe group consisting of Pb²⁺, Mn²⁺, Yb²⁺, Sm²⁺, Eu²⁺, Dy²⁺, and Ho²⁺,and C denotes a trivalent element selected from the group consisting ofY³⁺, La³⁺, Ce³⁺, Pr³, Nd³⁺, Pm³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺,Er³⁺, Tm³⁺, Yb³⁺, Lu³⁺, and Bi³⁺, with the proviso that at least twoelements selected from the group consisting of A, B and C have to bepresent, m+n++p=w, wherein m≥0, n≥0, p≥0 and q≥0, u+v=y, wherein v≥0,u≥0, 0≤w≤0.3, 0≤x<0.5, 0≤y<0.5, wherein at least two of w, x and v haveto be larger than 0, and 0<z<0.5.
 2. The compound according to claim 1,wherein T denotes Al.
 3. The compound according to claim 2, wherein w=0.4. The compound according to claim 1, wherein A denotes Eu²⁺.
 5. Thecompound according to claim 1, wherein B denotes Mn²⁺.
 6. The compoundaccording to claim 1, which is a compound of one of the followingformulae Ia-1 to Ia-7((Sr_(s)Ba_(r)Ca_(t))_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-1((Ca_(t)Ba_(r))_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-2((Sr_(s)Ba_(r))_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-3((Sr_(s)Ca_(t))_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-4(Sr_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-5(Ba_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-6(Ca_(1-x-u))(Mg_(1-z-v)Al_(z))(Si_(2-z)Al_(z))O₆:(Eu²⁺)_(x)(Mn²⁺)_(y)  Ia-7wherein 0<r<1; 0<s<1; 0<t<1; wherein r+s+t=1, u+v=y, wherein v≥0 and u≥0and wherein at least one of u and v has to be larger than 0, 0.1<x<0.3,0.1<y<0.2, and 0.05<z<0.4.
 7. The compound according to claim 1, whereinT denotes Al, A denotes Eu²⁺ and B denotes Mn²⁺.
 8. The compoundaccording to claim 7, wherein w=0.
 9. A process for preparing thecompound according to claim 1, comprising the following steps: a) mixinga silicon-containing agent, a mixture of salts comprising at least theelements of Mg, Al, M and T and one or more salts comprising at leasttwo elements selected from the group consisting of A, B and C at apredetermined molar ratio in a solvent; b) adding a precipitation agent;c) performing a primary heat treatment on the mixture in a temperaturerange of 800 to 1300° C. under an oxidative atmosphere; and d)performing a secondary heat treatment on the mixture in a temperaturerange of 800 to 1300° C. under a reductive atmosphere.
 10. The processaccording to claim 9, wherein the salts in step a) are selected from thegroup consisting of nitrates, halogenides, hydrogensulfates andcarbonates.
 11. The process according to claim 9, wherein theprecipitation agent in step b) is selected from the group consisting ofsodium hydrogen carbonate, ammonium chloride, and ammonium hydrogencarbonate.
 12. The process according to claim 9, wherein thesilicon-containing agent in step a) is an inorganic silicon compound oran organic silicon compound.
 13. A phosphor mixture comprising at leastone compound according to claim
 1. 14. An illumination unit, which hasat least one light source with an emission maximum in the range of 280nm to 400 nm, and all or some of whose radiation is converted intolonger-wavelength radiation by a compound according to claim
 1. 15. Theillumination unit according to claim 14, wherein the light source is aluminescent indium aluminium gallium nitride.
 16. A method forconverting UV or near-UV emission to longer wavelength radiation,comprising exposing said UV or near-UV emission to a compound ofclaim
 1. 17. A solar cell comprising a compound of claim 1 as awavelength conversion material.
 18. An illumination unit, which has atleast one light source with an emission maximum in the range of 280 nmto 400 nm, and all or some of whose radiation is converted intolonger-wavelength radiation by a compound according to claim
 6. 19. Amethod for converting UV or near-UV emission to longer wavelengthradiation, comprising exposing said UV or near-UV emission to a compoundof claim
 6. 20. A solar cell comprising a compound of claim 6 as awavelength conversion material.